1. Field of the Disclosure
The disclosure is generally related to permanent ink compositions and to writing instruments containing such ink compositions.
2. Brief Description of Related Technology
The writing performance of writing instruments including but not limited to ball pens, felt tip pens, fountain pens, and markers can be negatively affected by a phenomenon referred to as “dry out.” Dry out occurs because the ink composition contained in a writing instrument can evaporate from an exposed writing point, and leave a solid residue behind. The left over residue can result in the formation of a deposit that is capable of preventing a writing point, e.g., a ball point, from functioning properly, thereby causing the ball pen to write poorly or even fail. Similarly, the left over residue can clog the capillary tubes of fibrous ink reservoirs and/or fibrous nibs in writing instruments that rely upon capillary action, thereby causing such writing instruments to write poorly or even fail.
For this reason, consumers are often advised to cap writing instruments after use. Capping creates a substantially sealed atmosphere around the writing point, and thus lessens dry out. Alternatively, a writing instrument can be made to retract such that its writing point is substantially sealed after retraction—without need for a cap. Such capless retractable pens and markers are well known, and often use twisting or knock-type mechanisms to retract the writing point. However, dry out still can occur even when a can is used or a point of a writing instrument is retracted.
Existing ink compositions often include slow evaporating solvents (e.g., solvents having boiling points greater than about 115° C.), commonly referred to as humectants, in order to mitigate dry out. Such slow evaporating solvents, however, can negatively affect the permanence of n arks written with such ink compositions.